Keith Larson wrote on 12/27/2011 03:05:48 PM:
> Dear all,
>
> I would like to conduct a Pearson's correlation using cor.test
> separately for each individual in my data set. Each individual has
> nine observations of the measurement variable 'Delta13C'. I can figure
> our how to do it manually one 'Individual_ID' at a time, but I cannot
> figure out how to automate the process (a loop I am guessing). In
> addition, I would like to generate a new data frame that has the each
> individual's 'Individual_ID', the pearson correlation 'estimate', and
> the 'p.valve'.
>
> The output table would look something like:
>
> Individual_ID, estimate, p.value
> WW_08A_02, -0.7670675, 0.01586
> WW_08A_03, -0.02320767, 0.9527
>
> Code with sample data:
>
> ## Create sample dataset
> WW_Wing_SI <-
> structure(list(Individual_ID = c("WW_08A_02", "WW_08A_02", "WW_08A_02",
> "WW_08A_02", "WW_08A_02", "WW_08A_02", "WW_08A_02", "WW_08A_02",
> "WW_08A_02", "WW_08A_03", "WW_08A_03", "WW_08A_03", "WW_08A_03",
> "WW_08A_03", "WW_08A_03", "WW_08A_03", "WW_08A_03", "WW_08A_03"
> ), FeatherPosition = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4,
> 5, 6, 7, 8, 9), Delta13C = c(-18.67, -19.16, -20.38, -20.96,
> -21.61, -21.65, -21.31, -20.8, -21.28, -20.06, -20.3, -21.21,
> -22.9, -22.87, -21.13, -20.68, -20.58, -20.69)), .Names =
c("Individual_ID",
> "FeatherPosition", "Delta13C"), row.names = c(NA, 18L), class =
"data.frame")
>
>
> ## Create vector with unique individual IDs
> WW_Wing_Individuals <- unique(WW_Wing_SI$Individual_ID)
>
> ## Create temp dataset with for the first individual
> temp <- WW_Wing_SI_Spring[ which(WW_Wing_SI_Spring$Individual_ID ==
> WW_Wing_Individuals[1]), ]
>
> ## Create temp2 dateset with results of pearsons product-moment
> correlation (for the first individual)
> temp2 <- cor.test(temp$Delta13C, temp$FeatherPosition, method="pearson")
>
> Many Cheers,
> Keith
>
>
*******************************************************************************************
> Keith Larson, PhD Student
> Evolutionary Ecology, Lund University
> Sölvegatan 37
> 223 62 Lund Sweden
> Phone: +46 (0)46 2229014 Mobile: +46 (0)73 0465016 Fax: +46 (0)46
2224716
> Skype: sternacaspia FB: keith.w.lar...@gmail.com
# split your data frame according the the individual IDs
wing.list <- split(WW_Wing_SI, WW_Wing_SI$Individual_ID)
# then apply cor.test() with extract to each element of the list
t(sapply(wing.list, function(temp)
cor.test(temp$Delta13C, temp$FeatherPosition,
method="pearson")[c("estimate", "p.value")]))
Jean
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